Sit rep - just started significant extension and refurb work on 50's house, and now getting more and more entwined into the whole heat pump debate etc as we get closer to selecting a system and then get it installed. Original house has just blown rockwool cavity installation - prob over 40 years old, but it's there - and a prior extension circa 20 years ago has high density insulation slabs in the cavity as deemed by regs at that time. New extension doing similar, though specs of insulation may have improved, and this will leave some, but not many older parts of the building still forming outside walls. Opting in final refurb phase to add further insulation from the inside for these areas. Loft on the 'add insulation' list as well. Hardwood double glazing throughout, but now needing attention to address issues inc leaky areas, doors etc. Underfloor heating throughout ground floor, but will be a mix of underfloor and legacy rads upstairs. Total annual KwH usage circa 37KwH (dual fuel), and new build will add circa 20% area, so with headroom, think we'll be heading for circa 45 KwH requirement. All in all, fairly representative of a house that must be replicated 1000's of times across the UK. Mains gas, leccy (80A fuse I think - Western Power are checking out) and that about completes the picture.
EV on order, though delivery will be god knows when - last I heard was Sept this year, and will be replacing the gas boiler with an ASHP. As much PV as we can put on the roof is the intent, and not now opting for solar water.
Being recommended a Daikin Altherma 3 H HT based system, and tenders are out for supply, fitting, etc. This is a High Temperature system, and is proposed as the right solution considering the full picture of the house.
Wanting to ask if anyone has experience of this specific ASHP, and to generally ask if there are an other considerations we should be taking in to account. Slight concern that the HT spec will mean higher running costs, but not sure how much. Daikin suggesting not much more the low temp but not quantifying currently. Believe Julian Clarke has one of these, but as a newbie, I can't message him directly -think that's how it goes. Hi Julian, any comments ?
Great site, has to be the most informative on the internet for UK householders.
Mains gas, leccy (80A fuse I think - Western Power are checking out) and that about completes the picture.
As you're with WPD I have the distribution network data for your area, including the sizes of cable and local substation information. I can't publish that on an open Forum of course. But I've been given access so that we can have discussions to resolve problem sites.
So once we can work out if you can Direct Message me, I'll stand-by to help. I'd need a post-code to start the ball rolling.
Even if your single-phase supply must be constrained to 80A max (which it might), this forum is discussing other possible ways forward using hybrid off-grid battery storage.
Sit rep - just started significant extension and refurb work on 50's house, and now getting more and more entwined into the whole heat pump debate etc as we get closer to selecting a system and then get it installed. Original house has just blown rockwool cavity installation - prob over 40 years old, but it's there - and a prior extension circa 20 years ago has high density insulation slabs in the cavity as deemed by regs at that time. New extension doing similar, though specs of insulation may have improved, and this will leave some, but not many older parts of the building still forming outside walls. Opting in final refurb phase to add further insulation from the inside for these areas. Loft on the 'add insulation' list as well. Hardwood double glazing throughout, but now needing attention to address issues inc leaky areas, doors etc. Underfloor heating throughout ground floor, but will be a mix of underfloor and legacy rads upstairs. Total annual KwH usage circa 37KwH (dual fuel), and new build will add circa 20% area, so with headroom, think we'll be heading for circa 45 KwH requirement. All in all, fairly representative of a house that must be replicated 1000's of times across the UK. Mains gas, leccy (80A fuse I think - Western Power are checking out) and that about completes the picture.
EV on order, though delivery will be god knows when - last I heard was Sept this year, and will be replacing the gas boiler with an ASHP. As much PV as we can put on the roof is the intent, and not now opting for solar water.
Being recommended a Daikin Altherma 3 H HT based system, and tenders are out for supply, fitting, etc. This is a High Temperature system, and is proposed as the right solution considering the full picture of the house.
Wanting to ask if anyone has experience of this specific ASHP, and to generally ask if there are an other considerations we should be taking in to account. Slight concern that the HT spec will mean higher running costs, but not sure how much. Daikin suggesting not much more the low temp but not quantifying currently. Believe Julian Clarke has one of these, but as a newbie, I can't message him directly -think that's how it goes. Hi Julian, any comments ?
Great site, has to be the most informative on the internet for UK householders.
Thank you
SWS
Hello and welcome to the forum. I have no experience if Daikin but hopefully Julian and/or others will help. will help.
How big is your house? Do you mean 37-45 thousand kWh per year? That is a lot. Is that from your EPC? I think you'd have to have an unusually large and/or poorly insulated house to need more than 40 thousand kWh per year to heat it. That would cost a lot whatever fuel you use. A proper heat loss survey will confirm though. Some data below about average usage.
If you control your house like this it will be comfortable and at the lowest possible cost.
High temperature unit enable you to supply a higher temperature to the heating system. At the same flow temperature, they are usually slightly less efficient than standard units as they are optimised for higher temperatures. However, they are not efficient at higher temperatures. Heat pumps are not gas boilers, there performance is not directly related to the flow temperature. Heat pumps move heat from one place to another (from low temperature to a high temperature (working against the laws of thermodynamics)) just like a water pump pumps water up hill (working against gravity). Think about it in a different way:- if you are required to carry 1 bucket of water per minute, up one story or 3 stories, moving it up one story is a leisurely task and requires little exertion, however moving that bucket up 3 stories will take significant effort and exertion. the stories is your flow temperature and the exertion is your electricity bill.
High temperature heat pumps are very expensive to run at high temperatures, it can but it is very inefficient. Another analogy is:- your car can do 130 mph but it will cos in more ways than one, if you travel at 60 mph, it is efficient and will last. It really is as simple as that. Therefore, run your heat pump low and slow for long periods for best performance.
Solar thermal is an ethical decision if you install a heat pump and or PV. When the Thermal will supply enough heat for your water, your heat pump will have a COP of around 6. Therefor as Thermal will only supply 30% to 40% of your hot water requirement, it will take a very long time to pay it off. We do install solar thermal, but attach it to a ground source collector. This substantially increases the performance of a ground source heat pump.
@heacol Hi Brendan, are there any more flexible versions of those Blauberg extractors? The house I am buying has ceiling-mounted extractors in the bathrooms that vent via flexible ducting that passes through the attic space. Similarly, the kitchen extractor is the cooker hood that has hard plastic ducting running quite a way before reaching a wall. Only the utility room and small downstairs toilet have direct through-wall extractors where the Blauberg units would work in the way they show.
@kev-m thanks for the reply. Will check my background data re current KwH's. Got me slightly concerned. It will be quite a big house, but not absolutely massive. Will be 5/6 beds when finished, but rooms aren't that huge. Based on my own records over the past 5 years, we've averaged usage as below
@cycleneil I have installed them into the loft with a flex pipe. Just make sure the flex is as short as possible and can collect and discharge in to fresh air. The longer the pipe, the worse the performance will be. I was involved with the developement of these units some years ago untill BRE refused to test them. They are over 85% efficient if installed through the wall.
I have 1 in my bathroom and have no condensation isses at all.
@kev-m thanks for the reply. Will check my background data re current KwH's. Got me slightly concerned. It will be quite a big house, but not absolutely massive. Will be 5/6 beds when finished, but rooms aren't that huge. Based on my own records over the past 5 years, we've averaged usage as below
Maybe this just shows how leaky we are currently.
Well your gas is quite high but not extreme. Electricity is well above average for a gas heated home though. Worth a bit of investigation though. What is the floor area of your house?
@cycleneil, excellent question and you’ve pretty much described our house room by room as we have the issues with extractors. I didn’t realise you get “heat saving” options.
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